Abstract
Chemical investigation of the methanol extract of the Vietnamese marine sponge Ircinia echinata led to the isolation of six new 9α-hydroxy-5α,6α-epoxysterols: 5α,6α-epoxycholesta-7,22(E)-dien-3β,9α-diol (1), 5α,6α-epoxycholesta-7,24(28)-dien-3β,9α-diol (2), (24R)-5α,6α-epoxy-24-ethyl-cholesta-7-en-3β,9α-diol (3), 5α,6α-epoxycholesta-7-en-3β,9α-diol (4), (24S)-5α,6α-epoxyergosta-7,22-dien-3β,9α-diol (5), and (24R)-5α,6α-epoxy-24-methyl-cholesta-7-en-3β,9α-diol (6) along with the known 5α-6α-epoxysterols: 5α,6α-epoxystigmasta-7-en-3β-ol (7), 5α,6α-epoxystigmasta-7,22-dien-3β-ol (8), and 5α,6α-epoxyergosta-7-en-3β-ol (9). Their structures and their configurations were established on the basis of high resolution mass spectra and extensive 1D and 2D NMR spectroscopic data and by comparison with the literature. Their cytotoxic activity, evaluated against three human cancer cell lines, MCF-7, Hep-G2 and LU-1, revealed that only compounds 3 and 4 exhibited significant antiproliferative activity and compound 3 showed a selective inhibition towards the MCF-7 human breast cancer cells.
Highlights
Marine sponges of the genus Ircinia are known as a rich source of varied bioactive natural products, including fatty acids [1], steroids [2,3], sesqui- [4] and sester-terpenes [5,6,7], peptides [8], and macrolides [9,10]
13C nuclear magnetic magnetic resonance resonance (NMR) data showed that compound 2 shares the same Δ7 sterol nucleus as 1, with the presence of epoxy group at C-5/C-6 andand a hydroxyl group at C-9
1 H NMR data of compounds 1–6 recorded in CD3 OD
Summary
Marine sponges of the genus Ircinia are known as a rich source of varied bioactive natural products, including fatty acids [1], steroids [2,3], sesqui- [4] and sester-terpenes [5,6,7], peptides [8], and macrolides [9,10]. The marine biodiversity of the East Sea is considered to be among the most extensive in the world, but remains poorly understood and explored. Kiem et al reported the isolation of several furanosesterterpenes and six known sterols from the sponge Ircinia echinata collected at Co To, Mar. Drugs 2018, 16, 424; doi:10.3390/md16110424 www.mdpi.com/journal/marinedrugs. Kiem et al reported the isolation of several furanosesterterpenes and six known sterols from the sponge Ircinia echinata collected at Co. To, Quang Ninh, Vietnam [16,17]. We describe the (1–6), isolation and structural characterization epoxysterols from I. echinata (Order Dictyoceratida, Family collected at Bai Tu Long, of six new 9α-hydroxy-5α,6α-epoxysterols (1–6), together with Irciniidae) three known. Activity of the nine 5α,6α-epoxysterols was evaluated against different human tumor cell lines
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